Slewing mechanism for cranes



June 10, 1969 G. c. No 3,448,863

[WW MYUJIJJHJ WU [MUM Filed Aug. 24, 1967 Sheet of 5 I NVEN'TOR. 65am: 6. A/azz June 10, 1969 G. c. NOLL SLEWING MECHANISM FOR CRANES Sheet Filed Aug. 24, 1967 INVENTOR. 60R6 C A/ou BMW!!! ummm Filed Aug, 24 1967 WW V M INVENTOR.

mm GZZWGZ' 61/1 04; y BY N lfhd/ United States Patent ()flice 3,448,863 SLEWING MECHANISM FOR CRANES George C. Noll, North Ridgeville, Ohio, assignor to Koehring Company, Milwaukee, Wis., a corporation of Wisconsin Filed Aug. 24, 1967, Ser. No. 663,153 Int. Cl. B66c 23/84 US. Cl. 212-69 2 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION Field of the invention The invention relates to material handling apparatus such as derricking cranes, tower cranes, power shovels and similar machines having a chassis and a rotatable superstructure and wherein an operating boom n the superstructure is slewed by horizontal rotation of the superstructure about a fixed-pivot center on the chassis.

Description of the prior art Slewing mechanisms of generally two types have heretofore been used in machines of the mentioned character, namely one type affording partial revolution, and another affording full revolution of the superstructure on the chassis.

The partial revolution type of slewing mechanism readily lends itself to operation by hydraulic rams and may be produced at relatively low costs. The full revolution type, on the other hand, usually involves a ring gear drive, a rotary power source and a locking mechanism for securing the superstructure against rotation from its pivotally adjusted positions, all of which renders this type of slewing mechanism more intricate and expensive than the partial revolution type.

Attempts have been made during the past to produce a simplified form of full revolution slewing mechanism which requires no ring gear, rotary power source or locking device for the superstructure. The problem was to be solved by the use of complementary hydraulic swing rams which would furnish the driving torque for the superstructure. However, such previous attempts have failed to produce a practical and fully satisfactory mechanism, particularly in the matter of efliciency of operation and precision or rotary adjustment of the superstructure.

Summary of the invention The principal object of the present invention is to provide a crane or the like having an improved form of full revolution slewing mechanism.

More specifically, it is an object of the invention to provide an improved full revolution slewing mechanism incorporating complementary hydraulic swing rams to produce the required driving torque for the superstructure but which mechanism avoids the shotcomings and disadvantages of previously known mechanisms of that type.

Patented June 10, 1969 According to the invention, double acting swing rams are provided with an improved form of valve mechanism which will accurately control their operation and which will instantaneously reverse the flow of operating fluid substantially without throttling loss at or near the ends of the contracting and expanding strokes of the rams.

A further object of the invention is to provide an improved slewing mechanism of the above outlined character which is simple and sturdy in construction, reliable in operation and which may be produced at relatively low costs.

These and other objects and advantages are attained by the present invention, various novel features of which will become apparent from the description herein of a preferred embodiment of the invention and will be pointed out by the appended claims.

Referring to the accompanying drawings:

FIG. 1 is a diagrammatic side elevation of the chassis and superstructure of a mobile crane embodying the invention;

FIG. 2 is an enlarged diagrammatic view generally on line IIII of FIG. 1, illustrating a full revolution slewing mechanism;

FIGS. 3, 4 and 5 are schematic views of valve gear in various conditions of adjustment; and

FIGS. 6 and 7 are sectional views of a hydraulic double selector valve in different positions of adjustment.

FIG. 1 shows the over-all organization of a mobile crane comprising a wheeled chassis 1, a superstructure 2 mounted on the chassis 1 for rotation on a vertical axis 3 by means of a large diameter annular ball bearing 4. An operating boom 6 is mounted on the superstructure for rotation in unison therewith on the chassis 1.

The ball bearing 4 (FIG. 2) is of conventional construction and comprises an annular inner race 7 rigidly secured to chassis 1, and an outer race 8 rigidly secured to the frame 9 of the rotatable superstructure.

A hydraulic slewing mechanism is operatively interposed between the chassis .1 and the frame 9 of the superstructure. It comprises an upright journal 11 which is rigidly mounted on the chassis radially inward of the bearing 4 and in off-center relation thereto; and a pair of complementary double acting hydraulic swing rams 12 and 13 which react between the journal 11 and pivots 14 and 16, respectively, on the frame 9 of the superstructure. A piston rod 17 of the ram 12 and a piston rod 18 of the ram 13 are concentrically pivoted on the journal 11, and the pivots 14 and 16 which connect the cylinders 19 and 21 of the rams 12 and 13 at their barrel ends with the frame 9 are spaced equal radial distances from the center 3' of the bearing 4 and have a circumferential spacing of degrees from each other.

A hydraulic double selector valve 22 for controlling the admission of pressure fluid to, and its emission from, the ram cylinder 19 is mounted on the rotatable frame 9 adjacent the pivot 14, and an identical selector valve 23 is mounted on the frame 9 adjacent the pivot 16 and hydraulically connected with the ram cylinder 21 for controlling admission of pressure fluid to, and its emission from, the swing ram 13.

As shown in FIG. 6, the valve 22 comprises a housing having pump ports 24, 26, tank ports 27, 28 and two ports connected by fluid lines 29 and 31, with ram ports 30 and 35. Reciprocably mounted within the housing of valve 22 is a valve spool 32 which is axially adjustable to a ram expanding position as shown in Fig. 6 and to a ram contracting position as shown in FIG. 7. For purposes of explanation, FIGS. 6 and 7 each show two pumps P and two tanks T, but it will be understood that in actual practice a single pressure source P (FIG. 2) and a single tank T will be provided to supply pressure fluid to the pump ports 24, 26 and to receive discharge from the tank ports 27, 28.

An actuating mechanism for the spool 32 of the valve 22 is operatively connected with the ram cylinder 19, as shown in FIGS. 2-5, so as to adjust the valve spool to its ram expanding (FIG. 6) and ram contacting (FIG. 7) positions in response to pivotal movement of the ram cylinder about its pivot pin 14 in opposite directions.

When the ram 12 occupies the contracted dead center position in which it is shown in FIG. 2, the valve spool 32, as more clearly shown by the enlarged view of FIG. 3 occupies an axially shifted position midway between its ram expanding (FIG. 6) and its ram contacting (FIG. 7) positions or in other words, a neutral position in which it blocks the pump ports 24, 26 as well as the tank ports 27 and 28. From this neutral position the valve spool 32 is shiftable axially in one direction into its ram expanding position, and in the other direction into its ram contracting position by a rocker plate 33 which is connected with the frame 9 by an upright pivot pin 34. An adjustable length link 36 extends between the rocker plate 33 and the valve spool 32, a pivot pin 37 connecting the link at one end with the rocker plate 33 at a radial distance from the pivot pin 34, and a pivot pin 38 connecting the link 36 at its other end with the valve spool 32.

An over-center spring mechanism is operatively connected with the rocker plate 33 and the frame 9 and comprises a stem 39 secured to a swivel block 41; a vertical pivot pin 42 connecting the block 41 with the frame 9; a sleeve 43 telescopically engaging the stem 39; a forked abutment 44 secured to the sleeve 43 and straddling the rocker plate 33; a pivot 46 connecting the abutment 44 with the rocker plate 33, and a precompressed coil spring 47 surrounding the sleeve 43 and reacting between the abutments 41 and 44. In the condition of the parts as shown in FIG. 3, the pin 46 occupies a deadcenter position on the connecting line between the pivots 34 and 42, and the expanding pressure of spring 47 is taken up on the frame 9 by the pins 34 and 42.

As shown in FIGS. 4 and 5, the rocker plate 33 has a generally semi-circular cam notch 49 in cooperative relation with a stud 51 on a lever 52. A pivot pin 53 swingably mounts the lever 52 intermediate its ends on the frame 9, and the end of the lever opposite to the stud 51 mounts a clevis 54 by means of a pivot pin 56. The lever arm from the pivot center 53 to the stud 51 is about 3% times as long as the lever arm from the pivot center 53 to the pivot pin 56. The clevis 54 has a tapped bore for connection witha threaded rod 57 which is lockable in lengthwise adjusted position on the clevis by means of a locknut 58. The rod 57 has a forked head for connection to a side lug 59 of the ram cylinder 19 by means of a pivot pin 61.

The foregoing explanations with respect to the swing ram 12 and its associated valve gear analogously apply to the swing ram 13. That is, as shown in FIG. 2, the spool 32' of the valve 23 has an adjustable length link connection 36' with a rocker plate 33, and an over-center spring mechanism including a precompressed coil spring 47 is operatively interposed between the frame 9 of the rotatable superstructure and the rocker plate 33'. An actuating lever 52 pivoted at 53 on the frame 9 has a stud 51 in cooperative relation to a cam recess of the rocker plate 33', and an adjustable length link 54', 57 connects the lever 52 with a side lug 59' of the ram cylinder 21.

FIG. 2 shows the slewing mechanism in full lines at the left side, and in broken lines at the right side, the broken line position representing a 180 degree turn of the superstructure from the full line position about the vertical pivot axis 3 (FIG. 1). Also diagrammatically outlined in FIG. 2 is a hydraulic circuit including the valves 22, 23; a pump P, tank T, three position control valve 62, and a reversing valve 63.

The lever 52 and its link connection 54, 57 with the ram cylinder 19 are so arranged that the stud 51 on the lever 52 is positioned in the cam notch 49 of the rocker plate 33 when the ram 12 is in the contracted dead center position in which it is shown in full lines in FIG. 2. The rocker plate 33 is thereby locked against pivotal movement about the pin 34 from the position in which it is shown in FIG. 3 and in which it holds the valve spool 33 in its neutral position,

As further shown in full lines in FIG. 2, the ram 13 occupies a half-way expanded position and the valve 23 is in its ram expanding position when the ram 12 is in its contracted dead center position.

As shown in the hydraulic circuit diagram of FIG. 2, the fluid line 65 connects the valve 63 with the ports 24, 26 of the valve 22 and also with the ports 24, 26 of the valve 23. The fluid line 70 connects the valve 63 with the ports 27, 28 of the valve 22 and also with the ports 27, 28 of the valve 23. The ports 30 and 35 of the ram cylinder 19 are connected with the lines 29, 31, respectively, of the valve 22, and the ports 30' and 35 of the ram cylinder 21 are connected with the lines 31, 29, respectively, of the valve 23. That is, the connections of the cylinder 19 with the valve 22 are reversed with respect to the connections of the cylinder 21 with the valve 23. Accordingly, the superstructure will tend to rotate in the direction of arrow A in FIG. 2 due to fluid pressure admitted to port 30' at the barrel end of cylinder 21.

As the superstructure turns in the direction of :arrow A, ram cylinder 19 swings from its contracted dead center position about its pivot pin 14 in the direction of arrow B in FIG. 3, and the stud 51 is thereby moved out of the notch 49 of the rocker plate 33 in the direction of arrow C in FIG. 3. Such movement of the stud 51 turns the rocker plate 33 slightly clockwise about its pivot pin 34, thereby moving the pin 46 from its dead center position to the left as viewed in RIG. 3. As a result, the over-center spring mechanism will then force the rocker plate 33 and valve spool 32 into the FIG. 4 position and hold the valve spool in the ram expanding position in which it is shown in FIGS. 4 and 6. Rotation of the superstructure in the direction of arrow A in FIG. 2 by the ram 13 will therefore be assisted by the ram 12 when the shifted valve spool 32 admits pressure to the port 30 at the barrel end of cylinder 19.

When a degree turn of the superstructure from its full line position in the direction of arrow A has been effected by the complementary expanding action of the rams 12 and 13, the ram cylinder 19 will have swung from its FIG. 3 position into its FIG. 4 position, and the lever 52 will occupy the position in which it is shown in FIG. 4.

During the next 90 degree turn under continued expansion of the ram 12 the ram cylinder 19 swings back from the FIG. 4 position in the direction of arrow D into the FIG. 3 position, and the lever 52, rocker plate 33 and valve spool 32 will resume the condition in which they are shown in FIG. 3.

Shortly before the ram 12 arrives in its expanded dead center position in which it is shown in broken lines in FIG. 2, the lever 52, on its clockwise return swing from the FIG. 4 position moves the stud 51 into the cam notch 49 of the clockwise cocked rocker plate 33. During the final return swing of the lever 52 into the FIG. 3 position the stud 51 cams the rocker plate 33 anti-clockwise and thereby restores the pin 46 to its dead center position between the pins 34 and 42 at the moment the ram 12 arrives in its expanded dead center position.

Rotation of the frame 9 from the broken line position of FIG. 2 in the direction of arrow A is initially effected by contraction of ram 13 and then by the complementary action of both rams which tend to contract under fluid an citizen/1.111111 As the superstructure turns in the direction of arrow A beyond the broken line position in which its shown in FIG. 2, ram cylinder 19 swings from its expanded dead center position about its pivot pin 14 in the direction of arrow E in FIG. 5. A relatively short initial swing of the ram cylinder 19 from its expanded dead center position in the direction of arrow B causes the stud 51 to move in the direction of arrow F in FIG. 3 out of the rocker plate notch 49 in which it is located while the ram cylinder is in its expanded dead center position. Such movement of the stud 51 out of the notch 49 in the direction of arrow F cams the rocker plate 33 anti-clockwise and moves the pin 46 to the right of its dead center position as viewed in FIGS. 3 and 5. As a result, the over-center spring mechanism will then force the rocker plate 33 and valve spool 32 into the FIG. 5 position and hold the valve spool in the ram contracting position in which it is shown in FIGS. 5 and 7.

When a 90 degrees turn of the superstructure from its broken line position in the direction of arrow A has been efiected by the complementary contracting action of the rams 12 and 13, the lever 52 will occupy the position shown in FIG. 5. During the final 90 degree turn of the superstructure under continued contraction of the ram 12 and under expansion of the ram 13, the lever 52 will swing back from the FIG. 5 position into the FIG. 3 position. v

Shortly before the ram 12 arrives in its contracted dead center position while thesuperstructure turns in the direction of arrow A, the lever 52 on its anti-clockwise return stroke from the FIG. 5 position moves the stud 51 into the cam notch 49 of the anti-clockwise cocked rocker plate 33. During the final return swing of the lever 52 from its FIG. 5 into the FIG. 3 position the stud 51 earns the rocker plate 33 clockwise and thereby restores the pin 46 to its dead center position between the pins 34 and 42. At the same time, the valve spool 32 is restored from its ram contracting to its neutral position as shown by FIG. 3. Unless the flow of fluid pressure to the rams is interrupted by manual shifting of the valve 62 from its center position to the right or left, the ram 12 will then repeat its described operating cycle in endless succession.

From the foregoing explanations it will be apparent that the lever 52 and the adjustable length link 54, 57 provide a lost motion connection between the rocker plate 33 and the ram cylinder 19. The lost motion connection is operable to pivot the rocker and to throw the spring 47 and associated telescopic elements 39, 43 over-center in one direction and thereby cause shifting of the valve spool 32 from its ram expanding position to (-FIGS. 4 and 6) to its ram contracting position (FIGS. 5 and 7) in response to clockwise swinging movement of the ram cylinder 19 about its pivot center 14, as viewed in FIGS. 4 and 5; and to pivot the rocker and throw the spring 47 and associated telescopic elements 39, 43 over-center in the opposite direction and thereby cause shifting of the valve spool 32 from its ram contracting position (FIGS. 5 and 7) to its ram expanding position (FIGS. 4 and 6) in response to anticlockwise swinging movement of the ram cylinder 19 about its pivot center 14, as viewed in FIGS. 4 and 5.

In summary, the herein disclosed crane is of the type wherein a. superstructure is rotatably adjustable on a chassis by sequential expansion and contraction of a plurality of hydraulic rams which are pivotally mounted on the superstructure and have crank type actuating connections, respectively, with the chassis. -In the disclosed embodiment of the invention, such crank type actuating connections are alforded by the hearings on the outer ends of the piston rods 17, 18 and the upright journal 11 on thechassis. An actuating rocker for each valve rpm/1i p/Vu/a/j mull/an 0n the went/110111112; a 1121/! connection between each rocker and its respective valve spool is operative to shift the latter from one operative position thereof to another, and vice versa, by pivotal movement of the rocker alternately in opposite direction (FIGS. 4 and 5); over-center spring means are operatively connected with each rocker and the superstructure so as to pivot the rocker and urge the respective valve spool alternately into one or the other of its operative positions (FIGS. 6 and 7) by over-center throw of the spring means alternately in opposite directions. (-FIGS. 4 and 5); and lost motion connecting means between each rocker and the respective ram are operable to pivot the rocker and throw the spring means over-center alternately in said opposite directions (-FIGS. 4 and 5) in response to swinging movement of the respective ram alternately in opposite directions about its pivot center on the superstructure.

The valve 23, its operating mechanism and its fluid connections with the ram cylinder 21 are arranged in such a manner that the operating cycle of the ram 13 has a degree phase shift with respect to the operating cycle of the ram 12. The rams will therefore complement each other in producing a continuous powerful driving torque for rotating the superstructure at a relatively slow speed, such as two revolutions per minute.

Operation of the slowing mechanism in the direction of arrow -A in FIG. 2 may be initiated by shifting the manually operable valves 62, 63 to the positions in which they are shown in FIG. 2. If the valve 62 is shifted to the right from its turn initiating position, the pump P will be idled and the superstructure may pivotally coast in either direction. If the valve 62 is shifted to the left the pump will again be idled but turning of the superstructure will immediately stop and the rams 12 and 13 will be hydraulically locked and secure the superstructure against turning in either direction from its r-otatively adjusted position.

Flow reversal by shifting of the valve 63 reverses the direction of rotation of the superstructure.

While in the foregoing a preferred embodiment of the invention has been disclosed it should be understood that the invention is not limited to the disclosed form and details of construction.

It is claimed and desired to secure by Letters Patent:

1. In a crane of the type wherein a superstructure is rotatably adjustable on a chassis by sequential expansion and contraction of a plurality of hydraulic rams which are pivotally mounted on the superstructure and have crank type actuating connections, respectively, with the chassis, and wherein a hydraulic valve is operatively associated with each ram and includes an axially shiftable valve spool for controlling the flow of pressure fluid to and from the associated ram; the improvement comprising an actuating rocker for each of said valve spools pivotally mounted on said superstructure, a link connection between each rocker and its respective valve spool operative to shift the latter from one operative position thereof to another, and vice versa, by pivotal movement of the rocker alternately in opposite directions; overcenter spring means operatively connected with each rocker and said superstructure so as to pivot the rocker and urge the respective valve spool alternately into one or the other of its operative positions by. over-center throw of said spring means alternately in opposite directions; and lost motion connecting means between each rocker and the respective ram operable to throw said spring means over-center alternately in said opposite directions in response to swinging movement of the respective ram alternately in opposite directions about its pivot center on said superstructure.

2. A crane as set forth in claim 1 wherein said lost References Cited motion connecting means comprise a link pivot ally con- UNITED STATES PATENTS nected with the respective ram cylinder; a lever pivoted intermediate its ends on said superstructure; pivotal con- 1,137,208 4/1915 Heleshaw 212-41 necting means between said link and said lever at a 2,928,381 3/1960 MaoDonald 212-68 relatively short radial distance from the pivot center 5 FOREIGN PATENTS of the latter, and cam portions on said rocker element engageable with an end portion of said lever at a relative- 819864 9/1959 Great Bntam- 1y long radial distance from the pivot center of the latter EDWARD A SROKA Primary Examiner upon swinging movement said lever about its pivot center in opposite direction 10 HARVEY c. HORNSBY, Assistant Examiner. 

